This invention relates to a cutting blade for a surgical instrument.
The use of lasers is well established in opthalmology, otolaryngology, gynaecology, dermatology and plastic surgery. The types of lasers that are used are numerous and varied with the type of laser that is used for a particular surgical procedure depending upon the desired laserxe2x80x94tissue interaction.
Visible, ultraviolet and near infra-red laser light have been combined with surgical blades to provide precise control of the application of laser radiation and/or to provide a means of coagulating blood adjacent an incision. U.S. Pat. No. 4,126,136 of Auth et al. describes a transparent scalpel blade connected to a fibre optic waveguide which transports laser radiation to the blade. The blade, which is preferably formed of synthetic sapphire, emits laser radiation through the tapered cutting edge to photocoagulate the blood. U.S. Pat. No. 4,627,435 of Hoskins discloses a surgical knife formed of a diamond blade optically coupled to a Nd:YAG (neodymium:yttrium-aluminium-garnet) laser by a fibre optic bundle. The diamond blade is heated by the laser radiation to provide a cauterizing action while making the incision. The diamond blade may also be coupled to a visible laser to provide illumination for enhanced visibility of the incision site.
U.S. Pat. No. 4,693,244 of Daikuzono describes an artificial sapphire blade coupled to a quartz optical fibre to transmit radiation from a Nd:YAG laser. The sapphire blade is heated by the radiation to coagulate the blood at an incision made with a separate surgical blade. U.S. Pat. No. 5,320,620 of Long et al, describes a laser surgical device with a blunt light emitting element for coagulation. The blade, which may be formed of sapphire, silica or YAG, is coupled to an optical fibre for receiving laser energy. The blade may be coated with a high melting point material to absorb the radiation and heat the blade. U.S. Pat. No. 5,194,712 of Jones describes a single crystal diamond cutting tool with an anti-reflection coating bonded to the entry and exit faces of the cutting tool to provide efficient transfer of laser light, or to communicate laser light at the desired incision.
Of the different types of infra-red laser, which include CO2 and Nd:YAG, CO2 lasers are most widely used for surgical applications of ablation and cutting of tissue. Owing to its position in the far infra-red region of the electromagnetic spectrum, the CO2 laser cannot be delivered through quartz, fibre optics or silica or sapphire lenses, since these materials are opaque to 10 micron wavelength light and absorb infra-red laser radiation. Materials that are commonly used with CO2 laser light, both as lenses and as mirrors, including sodium chloride, potassium chloride, zinc selenide and germanium. CO2 laser light is typically directed through a series of mirrors in a complex articulating system- through which the light is delivered to a handpiece containing a lens which will allow the beam to be focused in a non-contact manner into the target location.
According to the invention there is provided a cutting blade for a surgical instrument comprising:
a body formed of diamond;
a cutting edge; and
refracting means provided at a position remote from the cutting edge through which laser radiation entering the body of the cutting blade is refracted away from a focal point.
The cutting blade may include a reflective surface formed within the body of the cutting blade which is positioned to reflect laser radiation entering the cutting blade through the refracting means towards the cutting edge of the blade.
Preferably, the reflective surface reflects the laser radiation by means of total internal reflection.
Typically, the reflective surface has a generally parabolic shape in cross-section.
Ideally, the parabolic shape of the reflective surface has a focal line generally in common with the focal line of the refracting means.
The generally parabolic shape of the reflective surface may be formed by a series of planar sections arranged adjacent to one another in a curved arrangement.
The laser radiation is typically infra-red laser radiation, more specifically the radiation emitting from a CO2 laser.
Conveniently, the refracting means is an optical lens.
In a preferred embodiment of the invention the optical lens may comprise a cylindrical concave surface formed in a face of the body of the blade.
The cutting edge of the cutting blade may be formed along the edge between two faces having an included angle between them of approximately 60 degrees or less, preferably 36 degrees.
According to the invention there is also provided a surgical blade incorporating a cutting blade as is described above.